Multiple venture investors in Sincerely confirmed the deal was much better than break-even and Sincerely co-founder and CEO Matt Brezina said "everyone made money," including his investors and the company's 14 full-time employees.

San Francisco-based Sincerely is best known for its photo-printing apps Postagram and Ink, which allow users to create custom postcards or greeting cards from their phones, then have the cards printed and sent to any snail-mail address, no stamps required.

Sincerely also created PopBooth, an app that makes digital, photobooth-style "strips" on mobile devices; Sesame, an app that lets users buy and send gift boxes from their phones to physical addresses; and software for mobile app developers who want to include photo-printing and shipping functionality in their own apps.

Bringing Sincerely's mobile technology and hip design sensibility into the fray at Provide Commerce parent company Liberty Interactive should help the e-commerce juggernaut reach new customers and revitalize stalwart brands, Mr. Shimojima said.

San Diego-based Provide Commerce does not yet operate a greeting cards store, but the industry generates between $7 billion and $8 billion a year in sales in the U.S. alone, according to the Greeting Card Association.

Mr. Brezina said his company decided to sell to Provide Commerce in order to leverage the larger company's logistical infrastructure, customer relationships and more. He also said: "I recruited people who dropped out of college to join my startup, and that has kept me up at night. Now they have a win on their resume, and nothing feels better to me as a manager."

According to the company, Sincerely delivered cards and gifts to more than 1% of households in America prior to its acquisition by Provide Commerce.

Mr. Shimojima said he expects Sincerely to become something of a mobile creative agency to help all of the firm's existing brands evolve a mobile presence. None of the company's brands offer a mobile commerce app so far, he said.

All 14 Sincerely employees are joining Provide Commerce, but Sincerely will remain a standalone brand run by Provide Chief Information Officer Brady Cale and Sincerely's co-founders Bryan Kennedy and Brezina in San Francisco.

Spark Capital General Partner Bijan Sabet, the first investor in Sincerely, said, "No question mobile is becoming more important to big companies." His firm is an investor in several other mobile commerce players including Proflowers competitor BloomNation and mobile furniture seller JossAndMain (operated by Wayfair.com). Spark plans to continue investing in mobile commerce and media companies, he said.

According to a recent study by Burst Media, 45.7% of U.S. adults online use smartphones and 41.3% use tablets to shop for holiday products and gifts.

This exit marks the second in a year for Sincerely's co-founders. A company they formed earlier, Xobni, sold to Yahoo in July for more than $40 million.

Sincerely raised $5.5 million in total venture capital prior to its deal with Provide Commerce. Its investors included several angel investors along with Charles River Ventures, First Round Capital, Spark Capital and SV Angel.